scope:

This Recommendation specifies error performance events, parameters and objectives for ODUk paths¹ of the optical transport network (OTN), as specified in [ITU-T G.709]. Clauses 1.1 to 1.3 give further details.

Application of this Recommendation

This Recommendation is applicable to international paths of the optical transport network as described in [ITU-T G.709]. These paths are at the ODUk layer of the OTN, and are digital paths (see [ITU-T G.709] for a description of the ODUk layer). While this Recommendation specifically addresses objectives for international ODUk paths, the allocation principles can be applied to the design of error performance for national or private paths.

The quality of client services, as well as the performance of the network elements belonging to the service layer, is outside of the scope of this Recommendation. However, ITU-T G.8201-based paths can carry various clients (e.g., SDH, ATM, GFP (i.e., IP, Ethernet, etc., encapsulated in GFP), etc.; see [ITU-T G.709]). ODUk paths meeting the objectives of this Recommendation will enable client layer traffic to meet its respective performance objectives.

The error performance objectives are applicable to each direction of the ODUk path independently. The values apply end-to-end over a 27 500 km hypothetical reference path (see Figure 3). The performance of multiplex and cross-connect functions of client layers of the OTN (i.e., higher layers, above the OPUk, e.g., SDH, ATM, etc.; see [ITU-T G.709] for a description of the OPUk) are not included in these values.

The parameter definitions are block-based with the block repetition rate in accordance with OTN technology, making in-service measurement convenient. In addition to in-service measurements, compliance with this Recommendation can be assessed using out-of-service measurements or estimated by measures compatible with this Recommendation as those specified in clause 7.

The objectives given in this Recommendation are long-term objectives to be met over an evaluation period of typically 30 consecutive days (one month). Shorter measurement periods required for maintenance and bringing-into-service are covered in [b-ITU-T M.2401].

Transport network layers

This Recommendation specifies the error performance of ODUk paths in a given transport network layer. In the context of this Recommendation, an ODUk digital path is a trail carrying an OPUk payload and associated OPUk and ODUk overhead through the layered transport network between the path terminating equipment (see Figure 1).

The scope of application of this Recommendation is from path-end-point to path-end-point as illustrated in Figure 2.

Allocation of end-to-end performance

Allocations of end-to-end performance of ODUk paths are derived using the rules laid out in clause 8.3, which are length and complexity based. Detailed allocations of ITU-T G.8201 performance to the individual components (sections, multiplexers and cross-connects, etc.) are outside the scope of this Recommendation but, when such allocations are performed, the requirements of clause 8.3 should be met.

¹ In this Recommendation, unless otherwise specified, the term path means ODUk path (k = 0, 1, 2, 2e, 3, 4 or flex). The nominal ODUk rates are approximately 1.25 Gbit/s for ODU0, 2.5 Gbit/s for ODU1, 10 Gbit/s for ODU2 and ODU2e, 40 Gbit/s for ODU3, 100 Gbit/s for ODU4 and a rate of 1.25 Gbit/s or more for ODUflex.